Tensioning device for belt or the like

Abstract

A hydraulic autotensioner of a sealed type is used to give tension to a belt or a chain. The hydraulic autotensioner includes a body member having a large diameter oil chamber, a plunger having a small diameter oil chamber and a small passage, a piston whose head extends outside the body member and a spring for biasing the plunger.

What is claimed as new and desired to be secured by Letters Patent of the United States is: 
     
       1. A hydraulic autotensioner of a sealed type comprising: a body member defining a large diameter oil chamber;   a plunger sealingly inserted in a movable manner in said body member, said plunger having a small diameter oil chamber formed in the center thereof and a small passage which communicates said large and small diameter oil chambers;   a piston sealingly inserted in said plunger in a movable manner, said piston having a head extending outside of said body member, said piston head having an end face defining a press face;   a spring in said body member for biasing said plunger in the direction of said large diameter oil chamber; and   a snap ring arranged at an opening of said body member and engaging said spring.   
     
     
       2. A hydraulic autotensioner of a sealed type according to claim 1 including a second spring in said small diameter oil chamber for biasing said piston outside of said body member. 
     
     
       3. A hydraulic autotensioner of a sealed type according to claim 1 including a check valve at the bottom of said small diameter oil chamber to control opening and closing of said passage. 
     
     
       4. The hydraulic autotensioner of a sealed type according to claim 1 in combination with a belt, wherein said press face forcibly contacts said belt. 
     
     
       5. The hydraulic autotensioner of a sealed type according to claim 1 in combination with a chain, wherein said press face forcibly contacts said chain.